Question

When a certain metallic surface is illuminated with monochromatic light of wavelength λ, the stopping potential for photoelectric current is 3V₀, when the same surface is illuminated with light of wavelength 2 λ, the stopping potential is V₀. The threshold wavelength for this surface for photoelectric effect is : M

(a) 6 λ

(b) 4 λ 3

(c) 4 λ 

(d) 8 λ

Answer 1

Correct option (c) 4 λ

Explanation:

Einstein’s equation for photoelectric effect is given by

hν = hν₀ + eV_s

where V_s = stopping potential In the first case,

Subtracting eq. (ii) from eq. (i), we get

Suppose λ₀ is the threshold wavelength, then from eq. (i) and (iii), we have